1. Field of the Invention
The present invention relates generally to fluid sampling apparatus and in particular to a dripless cannula system usable in connection with a fluid sampling site to minimize user contact with trace fluid occurring at the port during the fluid sampling procedure.
2. Discussion of the Prior Art
In a hospital setting there is always the need to monitor patient health through the evaluation of a blood chemistry profile. The simplest method employed in the hospital is to use a syringe carrying a sharpened cannula at one end and insert that cannula into a vein or artery to extract a blood sample from the patient. However, such a procedure exposes the patient to airborne bacteria and viruses which can enter through the opening made by the needle during the blood sampling process and the nurse or technician may be exposed to blood borne pathogens if they accidentally jab themselves with a used needle carrying such pathogens.
Moreover, it is an anomaly that the more seriously ill the patient is, generally the more often such blood sampling procedures must take place to monitor the blood profile and examine the level of pathogens in the blood. Accordingly, when an alternative to direct sampling from a vein or artery is available to the nurse or clinician monitoring the health of the patient that alternative is actively pursued. Thus the increased utilization of indwelling arterial or venous catheters in critically ill patients has lead clinicians to, whenever possible, use such arterial or venous lines for blood sampling.
To expedite sampling in such arterial or venous lines, stopcocks and injection sites or sampling ports have been provided in such lines to facilitate blood sampling. Stopcocks were added to facilitate blood sampling before sampling ports were used. However, stopcocks increased contamination and risk of infection and increased blood waste. Sampling sites eliminated many of the concerns associated with both directly drawing and using stopcocks to withdraw a blood sample from the patient. The catheter associated with such line was securely placed in the patient and needed to be placed only once to minimize pain, puncture wounds, the chance of damaging surrounding tissue and organs, and the possibility of infection to the patient caused by multiple samplings.
Thus in the earliest design of remote sampling sites to be placed in arterial or venous lines the focus was on infection to the patient and such lines were typically designed for use with sharp cannulae. Typically such sites were formed of a housing having a fluid flow path therethrough, with access to the fluid flow path provided through a membrane or septum disposed in the housing so as not to interfere with or impede such fluid flow path. An example of such a sampling port is shown in U.S. Pat. No. 4,673,648 entitled "METHOD AND APPARATUS FOR ARTERIAL AND VENOUS BLOOD SAMPLING" and issued Aug. 16, 1988.
The earliest uses of such sampling sites were with sharpened cannulae. The sharpened cannulae were forced through the septum to be placed into fluid flow communication with the fluid path through the housing. Repetitive piercing of the septum in such injection sites were a source of physical damage to the septum. Such damage, known as coring or laceration, could shorten the effective life of the injection site.
Moreover such an apparatus failed to eliminate the possibility of the nurse or clinician using a sharp cannula from being infected by blood borne pathogens caused by an accidental stick with the sharpened cannula following extraction of a blood sample from a patient.
Consequently, the next step in the evolutionary development of the dripless cannula was the development of a blunt cannula to be used with a sampling site. In such configuration the sampling site was also provided with a slit to facilitate insertion of the blunt cannula into the sampling site for extraction of a blood sample from the patient. The blunt cannula solved one part of the problem associated with a blood draw from a sampling site in that such blunt cannula would not pierce the skin of the user.
However, the possibility of infection by a blood borne pathogen to the user remains since the blood at the sampling site and in the syringe was typically under arterial or venous pressure seen at the sampling site or the distal tip of the cannula, and in extreme cases could cause a fine spray of blood to contact the user and thus still cause contact between the clinician or nurse treating the patient and the blood borne pathogens of the patient.
Accordingly, it would be desirable to so modify the sampling site and/or the cannula system associated with such sampling site for performing a fluid draw procedure at the site so as to minimize the possibility of blood droplets remaining at the sampling site following a sampling procedure while retaining all of the advantages inherent in a blunt cannula system usable with a resealable slit as such system has evolved from the earliest stages of blood sampling procedures.
Further it would be desirable if such improved sampling system comprise a simple adjunct to the blunt cannula requiring few additional parts, be integrally joined with the blunt cannula for simplicity of operation, and further enable simplicity of operation to minimize operator error in the blood draw process which would unnecessarily expose the clinician to blood borne pathogens.